I was crazy ambitious to try Bon Appetit’s recipe for Bûche de Noël two days before Christmas. And I should have been warned; anything that can go wrong will go wrong. I accidentally added too much cream to the mascarpone filling and ended up with cream soup instead of cream cheese. I needed a save. So I did a quick search and found Nick Malgieri’s recipe on Food Network for Bûche de Noël that called for a simple coffee buttercream filling. So I married parts of the two recipes together, using the BA recipe for cocoa syrup and sponge cake, and Malgieri’s coffee buttercream frosting. Figuring I was pushing my luck, I simply cut the log in two rather than try to decorate it.
Bûche de Noël (adapted from Bon Appetit and Food Network)
Make the Cocoa Syrup (makes 1/4 cup)
1/4 cup sugar
2 tablespoons cocoa powder
1 teaspoon rum
Cook sugar and ¼ cup water in a small saucepan over low heat, stirring until sugar is dissolved. Remove from heat; add cocoa powder and rum and whisk until smooth. Cool, cover and chill. Bring to room temperature before using.
Make the Coffee Buttercream (makes 3-4 cups)
4 (120g) egg whites, room temperature
1 cup superfine sugar
340g unsalted butter, cubed, room temperature
2 tablespoons instant espresso coffee powder
2 tablespoons dark rum
Dissolve the coffee powder in the rum and set aside.
Put 2 inches of water in a large saucepan on the stove and bring it to a simmer. Put the egg whites in the bowl of an electric mixer and whisk in the sugar. Place the bowl on top of the saucepan of simmering water—the water shouldn’t touch the bowl. Continue whisking the eggs whites until foamy and opaque, and the sugar dissolves. The egg white mixture should be warm to the touch and not at all gritty.
Remove the bowl and attach it to the mixer. Using the whisk attachment, whisk the egg white mixture on medium speed until the egg whites have cooled—the bottom of the bowl will be cool to the touch.
Turn off the mixer and switch to the paddle attachment. Add the butter a tablespoon at a time, beating on medium speed until the buttercream is smooth. Slowly pour the coffee mixture into the buttercream while the machine is still beating. The buttercream will curdle but keep beating because it will come together, about 1-2 minutes to completely blend in the coffee mixture.
Can be made a day ahead and refrigerated. Bring to room temperature then beat with paddle attachment on medium high speed until smooth and it comes together again.
Make the Sponge Cake
Melted butter for brushing the pan
1/4 cup all purpose flour
3 tablespoons cornstarch
1/3 cup unsweetened cocoa powder plus more for dusting
1/4 cup whole milk
3 tablespoons unsalted butter cut into pieces
1 tablespoon vegetable oil
1 teaspoon vanilla extract
1/4 teaspoon salt
3 large eggs, room temperature
3 large egg yolks, room temperature
3/4 cup sugar
Increase oven to 400°. Line a 12x17x1″ rimmed baking sheet parchment and brush melted butter on it. Flip it over and brush butter on the other side of the parchment and the pan sides and corners. Set aside
Whisk flour, cornstarch, and ⅓ cup cocoa powder in a small bowl. Set aside.
Bring milk, butter, oil, vanilla, and salt to a simmer in a small saucepan over medium-low heat. Keep warm over low heat. It should be body temperature.
Cake Baker’s Note: If the milk mixture is too hot it will cook the eggs. I tested a drop on the inside of my wrist.
Meanwhile, using the paddle attachment, beat eggs and egg yolks with an electric mixer on medium speed until smooth. Increase speed to high; beat until doubled in volume. With motor running, gradually add sugar; beat until very light and fluffy and mixture falls back on itself in a slowly dissolving ribbon (it should be at least quadrupled in volume), about 5 minutes.
Reduce speed to medium and gradually stream in milk mixture. Stop the machine and remove the bowl. Sift one-third of dry ingredients over the top of the batter; gently fold in until only a few streaks remain. Working in 2 additions, repeat with remaining dry ingredients, scraping bottom of bowl and using as few strokes as possible to keep eggs from deflating (a few streaks are fine). Scrape batter into prepared baking sheet and gently spread to edges of pan with an offset spatula. Tap sheet lightly on counter to pop any large air bubbles.
Bake cake until surface is puffed and springy to the touch, 10–12 minutes. Let cake cool in pan 2 minutes, then run a knife along edges to loosen. Spread a towel on a large work surface and sift cocoa powder on top. Invert cake on top of cocoa powder and carefully peel away parchment. Dust top of cake with more cocoa powder. Starting at one of the long sides, gently roll up warm cake inside towel. Let cake cool, seam side down, 30-35 minutes. Can be made 1 day ahead and stored tightly wrapped in plastic at room temperature.
Assemble the Bûche de Noël
Unwrap the thoroughly cooled cake and brush off any excess cocoa powder. Dab the cocoa syrup all over with a pastry brush. Spread about half of the coffee buttercream in a 1/2 inch layer, keeping away 1 inch from the longer edge opposite. Roll up the cake using the towel, but keep the towel on the outside. Chill, keep the seam side down, until filling is set, about 30 minutes. Don’t worry if there are any cracks in the cake; the frosting will hide it.
Transfer the cake to a serving plate. Evenly spread the remaining buttercream all over the cake. Using a serrated knife, trim 1/2 inch pieces from each end to create clean edges. Eat the trimmings!
If desired, create branches on the log by cutting off a 4 inch piece from one end. Cut it in half at a 45 degree angle leaving 1 inch at the opposite end. Attach the angled ends to the cake by using the remaining buttercream to attach the pieces and to fill in the spaces. Put one piece on top and the other on the side. Use an off set spatula to create the appearance of tree bark. Leave the cut ends unfrosted.